The filter is wonderfully effective, reading zero from the get-go, and producing noticeably higher quality results than any other brand on the market of which I am aware (e.g., Brita).  My only complaint with this model is that I can't seem to fill the tank more than about 1/3 of the way full, or else it will leak through the spout (almost as if the spout can't hold up to the water pressure).  I had a 23-cup model before that didn't experience this issue, so I'm not sure whether it's specific to the 20-cup, or I just got a faulty version.